Heat polymerization of vinyl halides



Patented Feb. 19, 1 946 HEAT POLYMERIZATION OF VINYL HALIDES Frank K. Sclioenfeld, Silver Lake, Ohio, assignor to The B. F. Goodrich Company, New York, N. Y., a corporation of New York No Drawing;

This invention relates to the polymerizationof.

vinyl halides, and has as its principal object'to decrease materially the time required to form the gamma (insoluble) polymers. a

It is well known that vinyl halides polymerize" to form thermoplastic resins. The polymeriza-.

tion may be carried out with vinyl chloride alone,

or in solution in many different types of solvent,

or dispersed in water or other immiscible liquid. Polymerization is catalyzed by actinic radiation or by per-compounds in general, including peroxides such "as calcium peroxide, barium peroxide, and benzoyl peroxide, per-acids such as persulfuric acid and per-salts such as the per borates, percarbonates, and perphosphates.

The type of polymer resulting from any of these processes depends to a great extent upon the temperature at which the polymerization is performed. Thus, at 40 C. the product consists mainly of the gamma polymer. Elevation of the temperature, however, greatly accelerates the formation of the soluble polymers. .When the polymerization is performed at 60 C. the product consists mainly of thealpha (most soluble). poly-.-

mer. On the otherhand, the rate of polymeriza-;

tion varies directlywith the temperature. :Thus;-

at 40 C. it may require '72 hours to'formthe.

gamma polymer from an emulsion of vinyl chloride containing benzoyl peroxide as a catalyst, while the polymerization may be completed in a third of this time at 60.

I have discovered that the rate of production of the gamma polymer may be increased materially by starting the polymerization at a temperature favoring the production of the soluble polymers, reducing the temperature to a temperature favoring the production of the gamma polymer before appreciable amounts of polymer are formed, and continuing the polymerization at the reduced temperature.

The particular temperatures employed will naturally vary with the particular vinyl halide. The length of time elapsing before the temperature is lowered depends upon the starting temperature. At the start of the polymerization process, there is a time lag during which no appreciable polymerization occurs. The polymer is formed very rapidly after polymerization starts,

Application February 10, 193 .Serial No. 189,891 i v 7 Claims. (01. 2e0-ss) during, the first 'four hours.

about 40 C., since at this temperature the gamma polymer is formed. It is to be understood that these temperatures are not critical, and that by applying the above principles, the optimum ternperature conditions for any polymerizationmay.

be obtainedam l r i Though th method of this invention may be applied to any method of polymerization of vinyl chloride, it is most conveniently applied to the polymerization ,of an emulsion of vinyl chloride in water. Any of the catalysts previously mer tioned maybe used, benzoyl peroxide being one of the best.- Any of the well-known emulsifying, dispersing or wetting agents may be used, typical examplesbeing the salts of the higher .alkyl sul fates, particularly those containing from 12to 18 carbon atoms, such-as sodium lauryl sulfate,

the s lts .ofialky na h ha ene ssliwkadsls @9911... as sodium isopropyl naphthalenefsulfonate and L, sodium di-isobutyl naphthalene sulfonate $939 such. as sodium .;cle ate and potasisurn .stearate ulsiYli1s;..

glue; glycol laur.ate,; etc.,-.- Mixtures of agents may also be employed.

As a specific embodiment of mydhven mnjtwt emulsions were prepared, each containing vinyl chloride 2500 gms., sodium lauryl sulfate 19 gms., sodium isopropyl naphthalene sulfonate 57 gms., benzoyl peroxide 25 gms., and water 3750 gins. Each charge was placed in a 2 gallon glass lined autoclave rotated end over end in a constant temperature bath. The first charge was run for 4 hours and 20 minutes at 60 C. The temperature was reduced to 40 C. within the next ten minutes, I

and the polymerization was continued for an :additional 43 hours and 30 minutes. product was washed to remove the emulsifying agents and dried, it was found that 83.5% of the vinyl chloride has been polymerized. The other batch was polymerized for 48 hours at 40 C., and produced only a 64% yield. Both products were uniformly finely divided. They were tested by incorporating grams of the polymer with 113 gms. of tricresyl phosphate and shaping in a heated mold to produce the resilient products described in the U. S. Patent 1,929,453 issued to Waldo L. Semon. Compositions formed from both polymers had good tensile strengths, proving that in both cases a large percentage of the gamma polymer had been formed.

The temperature should bereduced at the endof this time unless the batch is very carefully watched so thatthe temperaturec'an be reduced immediately when rapid polymerization starts. In the case of vinyl chloride, the-temperature is usuallyreduced to When the i In another experiment, emulsions similar to those previously prepared were polymerized under varying conditions. In the table below, the yields and the tensile strengths in lbs/sq. in. of compositions prepared from 150 parts or polymer and 113 parts of tricresyl phosphate as in the previous example are shown. 1

Hours polymerization at- Tensile strength Yield of polymer The low tensile strength of the product polyfavoring the production or the insoluble polymer before appreciable amounts oi polymer are formed, and continuing the polymerization {at the reduced temperature. i

2. The method which comprises heating a vinyl chloride emulsion in the presence of a catalyst at a temperature favoring the production 0! the soluble polymer, cooling to a temperature favorl ing the production of the insoluble polymer before appreciable amounts of polymer are formed,

, and continuing the polymerizationat the reduced temperature. a

' 3. The method which comprises heating vinyl chloride in the'presence of a catalyst at about 60 C., reducing the temperature to about 40 C. before appreciable amounts of polymer are formed, and completing the polymerization at I the reduced temperature.

merized at 60 C. for 24 hours is due to the large amount or soluble polymer present. It will be observed that by starting the polymerization at 60 C.'and reducing the temperature to 40 C. after 4 hours, the yield was increased 2 times, while the tensile strength remained'practically the same. It is obvious, therefore, that this invention provides a very satisfactory method of reducing the time necessary toeflect polymerization without deleteriously aiifecting the properties of the polymer.

, tions including substituting equivalent materials ,1 and varying the amountsof materials used are thespirit andfscope'of the inventionwas" defined in the appended claims.

I claim: a I

1. The method which comprises heating avinyl halide at a temperature favoring the production of the soluble polymers, cooling to a temperature 4. The method which comprises heating a vinyl chloride emulsion in the presence of. a catalyst at about 0., reducing the temperature to about 40 C. before appreciableamounts of polymer are formed, and continuing the polymerization at the reduced temperature. 0

5. The method which comprises heating a vinyl chloride emulsion in the presence of a oata-' lyst at about 60 C., reducing the temperature to about 40 C. after about 4 hours, and completing the polymerization at the reduced temperature.

6. The method which comprises heating a vinyl chloride emulsion in the presence 01' a cata lyst at a temperature favoring the production of the soluble polymer, cooling to a temperature favoring the production of the insoluble polymer before rapid polymerization starts, and continuing the polymerization at the reduced perature. v

7. The method which comprises heating a vinyl chloride emulsion in the presence of a catalyst at a temperature favoring the production of the soluble polymer until visible polymerization starts,

hnme'diat'ely icooling to a temperature favoring a l the production of the insoluble polymer, and con-- tinuing the polymerization at the reduced tem-- perature. FRANK K. SCHOENFEID; 

